This invention relates generally to wheel assemblies, and especially to wheel assemblies which are employed in ground-engaging drive systems which are used in e.g. tracked vehicles and in endless belt conveyors. While the disclosure herein focuses on tracked vehicles and endless track drive systems for such vehicles, it will be understood that the invention can be employed in other endless track drive systems.
Ground-engaging endless track drive systems in tracked vehicles employ a plurality of wheel assemblies to define a track path, which path is beneficially traversed by the track in causing the vehicle to move along the ground. Such track drive systems can include, for example and without limitation, on each side of the vehicle, a drive wheel assembly disposed adjacent e.g. the rear of the vehicle, an idler wheel assembly disposed adjacent e.g. the front of the vehicle, and one or more mid-roller wheel assemblies backing up the ground-engaging surface of the track between the drive wheel assembly and the idler wheel assembly.
In some embodiments, such track systems employ, as an additional element, one or more separate and distinct tensioning wheel assemblies in e.g. an upper portion of the track path. In other embodiments, the tensioning function is integrated into the operation of one or more of the other wheel assemblies, as a secondary function in addition to the primary function of the respective wheel assembly.
The structures of the several wheel assemblies are typically designed and configured according to the specific uses for which each such wheel assembly is to be employed. Accordingly, drive wheel assemblies are structured for their driving function.
Idler wheel assemblies are structured for their function of performing a significant angle turn of the track, and typically are structured to perform or assist with functions related to steering the direction of movement of the vehicle. Since the idler wheel assembly generally does not bear the stresses of driving the vehicle, on a given vehicle, the idler wheel assemblies are typically less complex, and may be less robust, than the drive wheel assemblies.
Mid-roller wheel assemblies are structured and mounted to provide downwardly-directed support of the underlying track, and thus can be spring loaded from the frame for such support of the endless track. Mid-roller wheel assemblies generally do not perform driving or steering functions.
Similarly, tensioning wheel assemblies, not shown in the drawings, are structured for typically upwardly-directed support of the track, and thus are also typically designed to be spring loaded from the frame. As with mid-roller wheel assemblies, tensioning wheel assemblies generally do not perform driving or steering functions.
Thus, while the drive wheel assemblies and the idler wheel assemblies, which perform driving and steering functions, are typically relatively more robust, and can be more complex, mid-roller wheel assemblies and tensioning wheel assemblies typically perform less demanding functions and thus can be somewhat less robust and may be simpler in design.
A variety of track widths are available for use with tracked vehicles. The typical practice in designing track drive assemblies for mass production of such vehicles is to provide wheels having a single common width in all such vehicles, irrespective of the track width which may be employed on a specific vehicle. The track width, on the other hand, is commonly specified on the basis of the anticipated use for which a particular vehicle is expected to be used. Exemplary of one factor which is commonly considered when specifying track width is weight bearing properties of the underlying surface over which the vehicle is to be used, Another factor is the ability of the project or operation to tolerate compaction of the underlying surface, e.g. soil. Still another factor is the traction properties of the underlying surface.
Thus, for example, a vehicle may be designed and constructed to receive an 8-inch wide track while some customers of such vehicles need to employ, for example and without limitation, 12-inch, 16-inch, or 24-inch wide tracks. Conventional practice is to retain, on the vehicle, the wheels built for the lesser width track (e.g. 8 inches) and to mount the wider width track on such wheels. However, in employing such strategy, the full benefit of the wider track is not achieved. Namely, the e.g. 16-inch wide track is mounted about the 8-inch wide wheels with e.g. the inner 8 inches of the track engaging the wheels while the remaining outer 8 inches of the track are not supported except from the inner 8-inches of the track.
Such cantilever arrangement of the additional width of the track can result in minor twisting of the track; and in the track accordingly applying an uneven pressure to the underlying e.g. soil, across the width of the track, whereby the e.g. outer unsupported portions of the track apply relatively less pressure to the underlying soil while the inner supported portions of the track apply relatively greater pressure to the underlying soil. Such uneven pressure partially compromises the above objectives of track design, namely attenuation of soil compaction, increased traction, improved distribution of weight, and the like.
It is desirable to have the track, as nearly as feasible on e.g. uneven surfaces over which tracked vehicles are commonly used, apply the same pressure to all areas of the soil or other surface over which the vehicle is run.
It is yet another objective to have the track, as nearly as feasible, run flat so as to avoid twisting of the track.
It is accordingly an object of the invention to provide an auxiliary wheel body to the wheel assembly whereby the auxiliary wheel body enables the resulting wheel assembly to accommodate and support a track which is wider than the main wheel body supplied as original equipment with the vehicle.
It is another object to provide a wheel assembly employing such auxiliary wheel body.
It is a further object to provide an endless track drive system employing such auxiliary wheel body on at least one of the wheel assemblies supporting the track.
It is still further an object to provide a tracked vehicle employing a track drive system having at least one wheel assembly which employs such auxiliary wheel body.
This invention comprises novel wheel assemblies for use in track drive systems in tracked vehicles, in support of improving uniformity of pressure distribution across the width of the track, between the track and the underlying ground surface, where track installed on the vehicle is wider than the wheel bodies which are supplied as original equipment with the tracked vehicle. Such improved uniformity of pressure is achieved by adding to the wheels of such tracked vehicle auxiliary wheel bodies which extend the widths of the wheels to widths more reflective of the width of the track being used in such vehicle. In cases where different track widths are sequentially employed on a given vehicle, auxiliary wheel assemblies of respective different widths are sequentially mounted, removed, and the like to reflect the widths of the tracks being employed.
To that end, the invention contemplates a wheel assembly for use in an endless track drive system. The wheel assembly comprises a wheel, which comprises a main wheel body and an auxiliary wheel body. The main wheel body has a first center of rotation, an inner flange defining a central opening for mounting the main wheel body to an axle for rotation of the wheel on such axle and about the first center of rotation, an outer flange having an outer surface, an inner surface, and first and second opposing sides, a first width of the outer surface between the first and second sides, and a web connecting the inner flange to the outer flange. The outer flange has a first overall width between the first and second opposing sides.
The auxiliary wheel body has an annular structure defining a second inner surface, a second outer surface, third and fourth opposing sides, and a second width of the outer surface between the third and fourth sides. The auxiliary wheel body is removably mounted to the main wheel, body, with the third side surface of the auxiliary wheel body disposed against the second side surface of the main wheel body. The combination, of the first width of the main wheel body and the second width of the auxiliary wheel body, defines a third overall width of the outer surface of the wheel. The third overall width is at least about 30 percent greater than the first width, preferably at least 50 percent greater, than the overall width of the main wheel body. In the illustrated embodiment, the overall width is 100 percent greater. The overall width can be multiples of the width of the main wheel body. For example, where the main wheel body is structured to support an 8-inch wide track, the auxiliary wheel body can provide structure capable of supporting a track up to 24 inches wide, or greater.
The auxiliary wheel body has a second center of rotation axially aligned with the first center of rotation.
The first and second outer surfaces of the main wheel body and the auxiliary wheel body in combination define an outer surface of the wheel having a generally common outer diameter, a central portion, and opposing ends at the first side of the main wheel body and the fourth side of the auxiliary wheel body.
The wheel assembly further comprises a tire comprising one or more tire bodies. The tire has an exterior. The tire exterior comprises an inner surface, an outer surface, and first and second side surfaces extending generally from the outer surface toward the inner surface. Each tire body comprises a plurality of cables proximate the inner surface of the tire body, embedded in the elastomeric material. The cables in combination are effective to strengthen the tire body and to limit radial stretching of the tire body.
The outer surface of the wheel receives the inner surface of the tire thereon at a wheel-tire interface.
The wheel assembly further comprises a first side flange at the first side of the main wheel body extending outwardly of the outer surface of the wheel to a distal edge inward of the outer surface of the tire, the first side flange comprising a first abutment surface facing away from the first side surface, and a second side flange at the fourth side of the auxiliary wheel body extending outwardly of the outer surface of the wheel to a distal edge inward of the outer surface of the tire, the second side flange comprising a second abutment surface facing inwardly of the fourth side surface. The second side flange, in some embodiments, faces the fourth side surface directly, as well as facing inwardly of the fourth side surface and toward the center of the outer surface of the wheel.
The first and second abutment surfaces of the first and second side flanges abut the first and second side-facing surfaces of the tire, thereby to effectively impede transverse movement of the tire off the wheel while the auxiliary wheel body is mounted to the main wheel body, while releasing such impediment such that the tire bodies can be removed transversely from the wheel when the auxiliary wheel body is dismounted from the main wheel body, and enabling subsequently sliding fresh such tire bodies onto the outer surface of the main wheel body and the auxiliary wheel body followed by again removably mounting the auxiliary wheel body to the main wheel body.
In some alternative but not exclusionary embodiments, the difference between magnitudes of the first and second diameters is greater than the radial stretch capability of the combination of the cables and the elastomeric material in the tire, thereby to prevent transverse movement of the tire off the wheel while the auxiliary wheel body is mounted to the wheel.
In some embodiments, the tire comprises a single tire body.
In other embodiments, the tire comprises more than one tire body. Typically, the tire comprises a limited number of tire bodies such as up to about 5 or 6 tire bodies over the full width of the tire. The tire bodies can have different widths whereby no two tire bodies need be the same width.
In preferred embodiments, the tire comprises a recess between the inner surface of the tire and ones of the first and second side surfaces, the recess defining a side-facing recess surface thereof, the first side flange comprising a relatively greater diameter portion of the outer surface of the wheel adjacent the respective first or second side of the wheel and including an abutment surface facing inwardly of the respective first or second side of the wheel, the abutment surface of the wheel abutting the side-facing surface of the tire thereby to impede transverse movement of the tire with respect to the wheel.
In some embodiments, the tire comprises first and second recesses between the inner surface of the tire and the first and second side surfaces, the recesses defining respective first and second side-facing recess surfaces thereof, the first and second side flanges comprising respective first and second relatively greater diameter portions of the outer surface of the wheel adjacent the respective first and second sides of the wheel and including first and second abutment surfaces facing away from the respective first and second sides of the wheel, the first and second abutment surfaces of the wheel abutting the first and second side-facing surfaces of the tire thereby to impede transverse movement of the tire with respect to the wheel.
In preferred embodiments, the outer surface of the tire defines the entirety of an outer surface of the wheel assembly.
Also in preferred embodiments, the wheel assembly is free from adhesive at the wheel-tire interface.
Still addressing preferred embodiments, the auxiliary wheel body preferably has apertures extending therethrough along the width thereof, receiving fasteners removably affixing the auxiliary wheel body to the main wheel body.
In highly preferred embodiments, the second side flange is an integral part of the auxiliary wheel body and comprises a relatively greater diameter portion of the outer surface of the auxiliary wheel body adjacent the fourth side.
Also in highly preferred embodiments, the first side flange is an integral part of the main wheel body and the second side flange is an integral part of the auxiliary wheel body, the first and second side flanges comprising relatively greater diameter portions of the outer surface of the wheel adjacent the first and fourth sides, and the tire optionally comprises first and second recesses in an exterior of the tire between the inner surface and the first and second side surfaces of the tire, the first and second recesses each defining a side-facing recess surface thereof, the first and second abutment surfaces of the first and second side flanges abutting the respective side-facing surfaces of the first and second recesses.
The invention also comprehends an endless track drive system, and a tracked vehicle. The drive system of such tracked vehicle comprises a prime mover, an endless track mounted about a plurality of wheels, and a drive train transferring drive power from the prime mover to at least one of the wheels, at least one of the plurality of wheels comprising a novel wheel assembly as described herein.
In such track drive systems and such tracked vehicles the wheel assemblies of the invention can be used e.g. as leading idler wheels, as mid-wheel rollers, and optionally as drive wheels.